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Vol. X November, 191 8 No. 6
DALDINIA VERNICOSA— A PYROXY-
Arthur S. Rhoads
(With Plate 14)
The collector is thoroughly aware that numerous species of
fungi occur prevailingly on burnt places. Although some of these
forms are found elsewhere occasionally, many are so constantly
associated with burnt places that they are sought only in such a
habitat. In order to account for this peculiar association many
plausible but inadequate reasons have been advanced. The fact
remains, as stated by Seaver (i), that sterilization of the sub-
stratum by heat apparently brings about some change in the soil
other than the simple elimination of competition in the destruc-
tion of bacteria and other fungi, which changes appear to be of
vital importance in the cultivation of fungi which normally grow
on a burnt substratum. Later experiments by Seaver and Clark
(2), dealing with the artificial cultivation of a species of Pyro-
nema, show that soil heated in various ways, especially by burning
over the surface, becomes a very favorable nutrient medium for
fungi of various kinds by reason of the large amount of food ma-
terial rendered available through the heating of the materials in
the soil. It is only natural to suppose that wood or bark, when
burnt, likewise becomes a more favorable medium for the growth
of certain fungi.
The writer has made several collections of Daldinia vernicosa
(Schw.) Ces. & De Not. in various states throughout the East and
generally finds it to be associated with fire-scorched trees. So far
[Mycologia for September (10: 231-275) was issued September 25, 1918.]
as can be determined this fungus is confined entirely to dicotyle-
donous trees but occurs upon a great number of species, prefer-
ably upon fire-scorched trunks. It attacks small saplings even
more readily than larger trees and seems to prefer species of
hickory for a host.
While making a survey of a burned area in the latter part of
August, 19 16, with a view to securing data in regard to the
rapidity of the deterioration of standing fire-killed timber by one
of our most common sap-rotting fungi, the writer was impressed
by the abundance of Daldinia vernicosa on the dead trees. An
area was selected near State College, Pa., that had been burned
for the first time, a surface fire having swept through it 1 year
and 3 months previously. As a result the trees on this area, with
few exceptions, were scorched so badly that they were killed out-
right. From this burned area an average sample tract, 100 by 500
feet, was laid off and the following data were secured for each
standing tree within this tract: species, diameter (measured to
the nearest inch) at breast height, conditions (as to whether dead
or living), and the species of fungi growing upon it as evidenced
by the sporophores upon the trunk. The species of trees upon
this tract in the order of their importance were white oak, scarlet
oak, white pine, mocker nut hickory, red maple, chestnut, and
pitch pine. The data obtained are given below, the trees being
tabulated by diameter under each species :
Out of 71 scarlet oak trees upon this tract only 1 bore sporo-
phores of Daldinia vernicosa. There also were present 15 red
maples, 6 chestnuts, 2>7 white pines, and 1 pitch pine but no trees
of these species bore sporophores. Out of a total of 363 dicotyle-
donous trees occurring upon this tract 46, or 13 per cent., bore
sporophores of Daldinia vernicosa within 1 year and 3 months
after the trees were scorched by fire. All the trees tabulated
above, save one, were dead at the time of the reconnaissance.
The above figures clearly indicate how extensively and rapidly
this ascomycete can propagate itself when afforded a favorable
substratum. The accompanying photograph (Plate 14, A), taken
in the latter part of August with a previous record of two months
of dry weather, testifies to the luxuriant growth made by the
Rhoads: Daldinia vernicosa
Summary of Trees Bearing Sporophores of Daldinia vernicosa by Species
D.B.H. inches! No. of trees on
Per cent bear-
of D. vernicosa
ti < t
»< 1 1
Quercus alba, total trees
Hicoria alba, total trees
sporophores of this fungus. Sporophores gathered and taken
into the laboratory at this time shed copious quantities of spores.
Associated with Daldinia vernicosa was another pyrenomycete,
Nummitlaria Bulliardi Tul. The stroma of this fungus is effused,
thin, and crustaceous. It overspreads the surface of the inner
bark, throwing off the epidermis for 6 inches or more in extent
and is black and carbonaceous at maturity. This fungus, how-
ever, was found only on the white oak and scarlet oak trees. It is
quite common throughout this region but always associated with
dead oak trees. It is not, however, so restricted to fire-killed trees
as is its associate, Daldinia vernicosa, but is apparently always
associated with dead trees, preferably oak trees.
The genus Daldinia is characterized by the peculiar structure of
the stroma, which is superficial, subglobose, and has a black and
carbonaceous external layer when mature, in which the perithecia
are imbedded. The stroma is softer inside, of a radiate-fibrous
structure and concentrically zoned.
There are 24 species of Daldinia, mostly from the tropics, given
in Saccardo. For the most part they can be referred to Daldinia
concentrica, which is a common and widely distributed plant oc-
curring in almost every country in the world. In Australia this
species assumes large size, frequently becoming two or three
inches in diameter as it sometimes does in the western United
States. In Europe, Daldinia durissima was proposed by Fries
many years ago, but, according to Lloyd (3), no one else ever
found it, a type at Kew being only the common D. concentrica.
Massee found a specimen in tropical America (Trinidad) which
he named Daldinia aspera. Lloyd, however, states that this spec-
imen is not a Daldinia (3) at all but a Hypoxylon, probably H.
cerebrinum (4). Leveille discovered two species in the United
States, D. cingulata and D. loculata, but Lloyd (3) states that
both are the common D. concentrica. Two well-known and ap-
parently distinct species of Daldinia occur within the United
States, namely D. concentrica (Bolt.) Ces. & De Not. and D. ver-
nicosa (Schw.) Ces. & De Not.
Peck (5), in his list of the plants of North Elba, reports Dal-
dinia vernicosa on dead trunks of young, standing deciduous trees.
He states that it is very doubtful if this and D. concentrica are
really distinct species, and is of the opinion that connecting forms
occur. It would appear that Peck had not collected Daldinia ver-
nicosa as typified by the specimens in the Schweinitzian her-
barium, for, if he had done so, it is difficult to see how such speci-
mens could be considered identical with D. concentrica.
The stroma of Daldinia concentrica is subglobose or hem-
ispheric, or rarely obovoid, while that of D. vernicosa is sub-
turbinate and sometimes contracted behind into a thick stipe-like
base which is often concentrically wrinkled. The stromata of
both species become black when mature, but that of D. vernicosa
becomes distinctly shining. When young and immature the
stroma of D. vernicosa contains a large quantity of a colorless
gelatinous substance which dries down at maturity, forming the
radiate-fibrous substance between the concentric zones. At ma-
turity practically all of the substance between the thin, blackish,
concentric zones under the terminal, monostichous perithecial
layer is made up of a colorless, radiate-fibrous, dry-gelatinous
Rhoads: Daldinia vernicosa 2&1
substance. It is thus seen that the interior of the stroma of this
plant is of a very heterogeneous texture. As a result of the loose
texture of the radiate-fibrous inner substance the mature fruit-
bodies can be crushed readily between the fingers. In Daldinia
concentrica the interior of the stroma also is of a radiate-fibrous
structure. Owing to its more homogeneous structure, however, it
is fairly firm and solid, and specimens that have not been attacked
by insects are very resistant to crushing. In the latter plant the
radiate-fibrous substance is brown instead of colorless, as it is in
Fig. i. Spores of Daldinia vernicosa showing various stages in the dehis-
cence of the exospore wall after treatment with dilute KOH ; a, spore at time
of shedding; b, spore showing the initial step in the dehiscence of the exo-
spore wall ; c and d, spores showing the casting off of the exospore membrane ;
e, cast-off exospore membranes, some with the valves still hinged together; /,
a later stage of e, showing the return of the two valves to their original posi-
tion. X 500.
D. vernicosa (Plate 14, B), and the concentric zones are not so
sharply defined as those of the latter species. As pointed out by
Ellis and Everhart (6) the perithecia of D. concentrica are
monostichous and not polystichous as stated by Saccardo. But
little difference is exhibited by either the perithecia, asci, or spores
of the respective species. The spores of D. concentrica are ob-
liquely uniseriate with the ascus, inequilaterally elliptical, dark-
brown, and finally opaque. They are somewhat variable in size
but usually conform to 12. 5-18 n by 7-10 /x. The spores of D.
vernicosa are about the same size as in the preceding species but
are somewhat smaller and less variable in size. They usually con-
form to the limits of 1 0-14.5 //, by 7-7.5 /*.
The spores of Daldinia vernicosa are peculiar in that, when
mounted in dilute (5 per cent.) KOH or NaOH, the exospore
wall, which is colorless, quickly dehisces and separates from the
spore, which is dark-brown. A single peripheral line of dehiscence
occurs at the center of the spore and the two halves of the exo-
spore wall usually break away from one another as two valves,
or they may dehisce partially and bend backward as if they were
hinged, thus allowing the spore to free itself from its peripheral
membrane (Fig. 1). The spores of Daldinia concentrica also ex-
hibit the same behavior, and, with equal facility. These obser-
vations on the dehiscence and shedding of the colorless exo-
spore wall of these two species, when the spores have been
mounted in dilute solutions of KOH and NaOH as well as certain
other dilute alkaline solutions, have been confirmed by the careful
and repeated examination of specimens from widely distant points
in several localities. This dehiscence of the exospore wall is less
evident, however, in old herbarium material.
Ellis and Everhart (6) sum up the differences between Dal-
dinia vernicosa and D. concentrica as follows: "This (D. verni-
cosa) is distinguished from D. concentrica by its shining-black
stroma, and the looser texture of the radiate-fibrous inner sub-
stance which is cut by 8-12 dark-colored, membranaceous hori-
zontal plates or layers. These are very noticeable in a vertical
section even in the young plant, while it is still covered with the
conidial layer and before the terminal, subglobose, ascigerous
stroma has begun to appear. In the mature state, the fibrous inner
substance and the horizontal membranes disappear to a greater
or less extent, and leave the stroma more or less hollow, so that
it may be easily crushed with the fingers, but in D. concentrica
the inner substance remains firm and is also of a darker color. "
Daldinia concentrica, according to Lindau (7), is of cosmo-
politan occurrence on dicotyledonous wood, while D. vernicosa,
according to Saccardo (8), is less widespread in its distribution.
In addition, the latter species generally occurs on burned woody
stems, whereas the former species does not seem to be pyroxylo-
It is often very difficult to secure mature specimens of D. con-
Rhoads: Daldinia vernicosa 283
centrica, and sometimes exceedingly difficult to secure mature
specimens of D. vernicosa that are free from insects. Even after
excellent specimens are collected, the interior portions of the
stroma usually are eaten out by the larvae that hatch out within
the specimens, unless they are quickly oven-dried.
In addition to his own collections the writer has examined spec-
imens of both plants in the herbaria of Dr. L. O. Overholts, The
Pennsylvania State College, The New York State College of For-
estry, Office of Pathological Collections in the U. S. Bureau of
Plant Industry, the Schweinitzian herbarium in the Academy of
Natural Sciences at Philadelphia, and the collections of the Office
of Investigations in Forest Pathology. The Schweinitzian her-
barium contains the type specimens of Daldinia vernicosa, which
were first described as Sphaeria vernicosa by Schweinitz from
specimens collected at Salem, North Carolina.
i. Daldinia vernicosa, as is typical of certain other fungi, oc-
curs prevailingly on a substratum of burnt wood, and is to be re-
garded as a pyroxylophilous fungus.
2. In its occurrence, it apparently is confined to dicotyledonous
species and attacks fire-killed saplings, particularly those of hick-
ory, with great vigor.
3. Out of a total of 363 dicotyledonous trees occurring upon
an average sample tract ( 100 by 500 feet) of a burned area, 46, or
13 per cent., bore sporophores of Daldinia vernicosa within 1
year and 3 months after the trees were scorched by fire.
4. Of the 24 (mostly tropical) species of Daldinia given in Sac-
cardo, most of them can be considered as mere growth forms or
ecological expressions of Daldinia concentrica, a widely distributed
plant of cosmopolitan occurrence.
5. Only two species of Daldinia occur in the United States, D.
concentrica and D. vernicosa, which appear to be morphologically
6. The dehiscence, of the colorless exospore wall occurs along
a single central peripheral line and seems to be a characteristic
feature of regular occurrence with the spores of both Daldinia
vernicosa and D. concentrica, when mounted in dilute alkaline
Office of Investigations in Forest Pathology,
Bureau of Plant Industry,
Washington, D. C.
i. Seaver, Fred J. Studies in pyrophilous fungi — I. The occurrence and
cultivation of Pyronema. Mycologia i: 131--139. pis. 9-12. 1909.
2. Seaver, Fred J., and Clark, Ernest D. Studies in pyrophilous fungi — II.
Changes brought about by the heating of soils and their relation to the
growth of Pyronema and other fungi. Mycologia 2: 109-124. pis.
24-26. 19 10.
3. Lloyd, C. G. Daldinia vernicosa. In Mycological notes. No. 43, p. 604.
4. Lloyd, C. G. Hypoxylon cerebrinum. In Mycological notes. No. 42, p.
5. Peck, C. H. Plants of North Elba, Essex Co., N. Y. New York State
Museum Bui. 6: 67-266. 1899. (See p. 229.)
6. Ellis, J. B., and Everhart, B. M. Daldinia vernicosa. In The North
American Pyrenomycetes, p. 661. 1892.
7. Lindau, G. Daldinia DeNot. In Engler and Prantl's Die natiirlichen
Pflanzenfamilien. Teil I, Abteilung I, p. 487. 1897.
8. Saccardo, P. A. Daldinia vernicosa. In Sylloge. Vol. i, p. 394. 1882.
Explanation of Plate 14
A. Trunk of white oak (Quercus alba L.) one year and three months after
it was killed by a light surface fire, showing the abundance of Dalidinia verni-
cosa. The trunk bears a 6-inch rule.
B. Sporophores of Daldinia vernicosa, showing both external and sectional
views, natural size.
Volume io, Plate 14
DALDINIA VERNICOSA (Schw.) Ces. and De Not.